The invention relates to a method for interconnecting, in three dimensions, packages or circuits containing at least one electronic component.
The production of present electronic systems must take into account increasing requirements for compactness, because of the increasing number of circuits used, and for fast operation. With the aim of compactness, the production of stacks of integrated circuit chips, as described in French patent FR 2 670 323, or of packages encapsulating semiconducting chips, as described in French patent FR 2 688 630 has already been proposed, the wafers or packages being interconnected in three dimensions by using the faces of the stack as interconnection surfaces.
However, since these blocks of stacked packages or circuits are then generally encapsulated with an electrically insulating material then shielded by depositing a metallization layer, there are not inconsiderable parasitic capacitances between the connections traced on the surfaces of the stack and the shielding. This is a significant drawback, especially when seeking fast operation of the components.
The object of the present invention is to overcome this drawback by interconnecting the conductors of the packages or circuits no longer by connections traced on the surfaces of the block but by connections making use of grooves perpendicular to the face of the block.
According to the invention, a method of interconnecting, in three dimensions, packages or circuits containing at least one electronic component and fitted with connection conductors is provided, in which said packages or circuits are stacked and secured by encapsulation using an electrically insulating material in order to form a block, said method being characterized in that it comprises the following steps:
a) cutting the block while leaving the ends of the conductors set back from the corresponding faces of the block;
b) cutting grooves into said faces and perpendicularly thereto, which grooves just clip the end of said conductors, respectively;
c) metallizing the block and its grooves;
d) polishing said faces of the block in order to remove the metallization from these faces;
e) encapsulating the entire block with an electrically insulating material.
The invention also provides an electronic device for interconnection in three dimensions comprising packages or circuits containing at least one electronic component and fitted with connection conductors, in which said packages or circuits are stacked and encapsulated with an electrically insulating material in order to form a block, characterized in that the ends of said conductors are set back from the corresponding faces of the block, in that said faces comprise grooves which just clip the respective ends of said conductors and the faces of which are metallized and in that said block comprises an electrically insulating material encapsulating the entire block and grooves.
Using these arrangements, only the cross sections of the metallizations of the grooves are flush with the surface of the block facing the shielding metallization, hence a considerable decrease in the parasitic capacitances. Furthermore, the fact that all the inner lateral surfaces of the grooves are metallized and contribute to the conduction markedly increases the cross section of the connections and therefore the possibilities of routing large currents without also increasing the separation of the connections.
Another aspect of the invention consists in taking advantage of the grooves thus obtained in order to produce supply busbars with a distributed capacitor thereby forming, by cutting the bottom of a groove, two mutually facing electrodes for the ground-supply system.
According to this other aspect of the invention, a method of the above type is therefore provided, characterized in that, during step b), at least one predetermined groove of said grooves just clips the end of two adjacent conductors supplying said packages or circuits and in that said method further comprises, between steps c) and e), the insertion of a step of:
g) cutting, in the bottom of said predetermined grooves and over their entire length, second grooves.
The invention also provides a device of the above type, characterized in that predetermined grooves just clip the ends of two adjacent conductors and in that the metallization of the bottom of said predetermined grooves is interrupted over the entire length of said grooves.
Thus it is possible to obtain modules with an integrated or hybrid busbar of small size and at low cost.